1. Field of the Invention
The present invention relates to vibration sensors and, more specifically, to a self-powered vibration sensor.
2. Description of the Prior Art
One out of ten people suffers from hearing loss. Such hearing loss ranges from mild impairment to complete deafness, both in children and adults. Hearing aid devices offer people with hearing loss a way to improve their hearing, thereby improving the quality of their lives. Typically, there are two categories of hearing loss, conductive hearing loss and sensorineural hearing loss (SNHL). For a conductive hearing loss, sound is not properly transmitted through the ear due to a structural defect. In such as situation, an amplifier may restore normal hearing.
The cochlea is the auditory portion of the inner ear and is filled with a watery liquid, which moves in response to the vibrations coming from the middle ear via the oval window. As the fluid moves, thousands of “hair cells” are set in motion and convert that motion to electrical impulses that are communicated to many thousands of nerve cells via neurotransmitters. The primary auditory nerve cells transform the auditory signals into electrical impulses known as action potentials. The action potentials travel along the auditory nerve to the brain, where they are perceived as sounds.
Cochlear hair cells in the inner ear serve as receptors for all auditory signals heard by the human ear. Essentially, each hair cell acts as a biological strain gauge. The vibration of the auditory signals applies a mechanical force on the hair cell, which opens an ion conducting channel in a cell membrane coupled to the hair cell. The flowing of ions through the channel result in an influx of current, which changes a potential associated with the membrane. The potential change affects the rate of release from the hair cell of a synaptic transmitter. Consequently, a pattern of action potentials which encode the auditory signals, including information such as intensity, time course and frequency, are transmitted to the brain via an afferent nerve fiber contacting the basolateral surface of the hair cell.
SNHL is often caused by the damage to the hair cells in the inner ear that are used to sense vibration, which causes a cochlear malfunction. One method of improving hearing in people with SNHL is through digital signal processing by pre-processing sound signals and amplifying certain frequencies. However, devices embodying this approach are of relatively large size and tend to have a high rate of power consumption.
Therefore, there is a need for a vibration sensor that mimics the function of hair cells, that is compact and that consumes relatively little power.